There is currently a bug with thorns on the crusader resulting in OP builds capable of 300m crits+ - THIS WORKS ONLY ON THE HIGHER DIFFICULTIES because for some reason it scales insanely so try this on t6.
Here is the blue post that confirms it:
Thorns too OP? - Forums - Diablo III
How to:
1) Get on torment 6 on your crusader
2) get iron maiden passive
3) use iron skin - reflective skin rune
4) additional thorns damage from gear may help
5) farm elites and profit
I believe this is going to be fixed quickly - use it fast.